The present invention relates to a quantizer for a so-called difference pulse code modulation ("DPCM") encoder having a read-only memory ("ROM"). In a quantizer of this type, the raw DPCM signal values are supplied to the address input of the ROM and quantized DPCM signal values are read out from the data output of the ROM as code words.
Difference pulse code modulation ("DPCM") encoders are used for encoding and compressing digital data; i.e., for data reduction. The quantizer in a DPCM encoder assigns a single output code word to a number of different data words presented at its input. The individual code words forming the quantized DPCM signal values are then supplied at the output of the DPCM encoder, usually after another code conversion.
The quantizer may be constructed, for example, as a hard-wired logic gate circuit. However, a read-only memory (ROM) may also be used. In the latter case, an extremely large memory space must be provided since each possible input value of the quantizer represents a distinct address for the ROM.